Passenger vehicles generally include a compartment or dome light which is illuminated when the vehicle door is opened and extinguished when the vehicle door is closed. A manual switch within the vehicle can illuminate the compartment or dome light when the vehicle door is closed. Recently, it has become somewhat common practice to provide a time delay feature for the dome light. As the door is closed, the dome light, which may include more than one simultaneously operated light, remains on for a preselected time. At first, these time delay devices employed relay or other mechanical contact circuits which required periodic maintenance and had to be replaced in some instances due to corrosion of the contacts and other deteriorating conditions. Since these systems control the dome light or lights, their deterioration often involves incapacitating the dome light itself which can be annoying and defeats the purpose of the time delay feature. To overcome the disadvantages of relay systems for controlling the time delay of the compartment or dome light operation, solid state timing circuits have been developed. These solid state timing circuits have often involved only a conversion of the basic relay circuitry into solid state components. Such systems have been used successfully; however, there is always a need from both a sales standpoint and a safety and convenience standpoint to provide improved circuitry for controlling the compartment or dome light or lights in a manner more concomitant with the actual needs of a passenger operating the vehicle.
In prior time delay circuits for controlling compartment or dome lights, the light remains illuminated for a preselected time following closing of the vehicle door. This may be desired in certain instances; however, if the door remains opened for a prolonged time, which can happen easily easily during daylight hours, there can be a substantial drain on the battery of the vehicle. In addition, most prior time delay circuits for controlling the compartment light, whether an electro-mechanical system or a solid state circuit, have required dissipation of at least substantial energy during steady state conditions. With the present amount of energy being required to operate a vehicle, this drain of energy is not desirable. In addition, this power consumption can cause a reduction in the overall life of the control circuit.